Variations 
var. treleasei
This variation is distinguished by segments having spines in areoles towards the top or it may have none.

var. basilaris
This variation is distinguished by broad obovate to sub orbicular erect segments with 10-16 areoles arranged in a diagonal row across the mid-stem segment.

var. longiareolata
This variation is distinguished by spathulate segments with an obtuse apex and 4-8 areoles arranged diagonally across the mid-stem segment.

var. brachyclad
This variation is distinguished by oblong to narrow spathulate segments with a truncate apex and 4-7 areoles arranged in a diagonal row across the mid-stem segment.  This cactus is commonly found in southern California.